In a wireless communication system, Transmission Control Protocol/Internet Protocol (TCP/IP) is used to assure the reliability of data communication. Accordingly, an interactive service that enables a plurality of nodes to exchange a signal with each other is provided in the wireless communication system. A signal may be transmitted/received on a packet-by-packet basis between the plurality of nodes, and the signal transmitted/received on a packet-by-packet basis may include data, a control signal, or the like. For convenience of description, data and a control signal will be hereinafter referred to collectively as a “packet signal”.
Upon receiving data, a first node transmits an Acknowledgement (ACK)/Negative acknowledgement (NACK) signal, which is a control signal, in response to the received data. Then, a second node determines whether or not to further transmit data to the first node, based on the ACK/NACK signal received from the first node, and continuously transmits data to the first node according to a result of the determination. With regard to this, the second node controls the flow of data while transmitting data up to the TCP window size before receiving the ACK/NACK signal.
The higher the data transmission speed, the greater the number of ACK/NACK signals to be handled, which may cause a problem in that data transmission is delayed. TCP/IP has been developed based on a wired communication system, and thus many other problems may also occur in a wireless communication system using TCP/IP.
For example, since a data loss rate is high in a wireless communication system, values expected for several parameters necessary for data transmission are much larger than those in a wired communication system. As a result, there is a problem in that communication cannot be smoothly performed due to delayed data transmission or delayed ACK signal transmission, and the overall throughput is also decreased.
At present, a message format and the like according to the TCP/IP standard are used in a wireless communication system that uses one service through a PPP connection or Ethernet connection, but various parameter values sensitive to time are now in use without any modification. Further, since all packet signals generated for one service have the same priority, it is impossible to packet signals according to priority.
As an example, although a control signal may be transmitted prior to data, the control signal has the same priority as data, and thus cannot be transmitted prior to data. Accordingly, the upper level layer (that is, application layer) of the first node delivers data to the lower level layer (that is, L1/L2/L3 (TCP/IP) layer of a protocol stack) in order of generation, and the lower level layer transmits the delivered data in order of delivery from the upper level layer.
In this way, it is impossible for the lower level layer to determine if a packet signal to be transmitted should be preferentially transmitted unless there is an indicator indicating whether or not the packet signal has high priority. Further, when many packet signals queued in the lower level layer wait for transmission, the packet signals are sequentially transmitted in order of generation, which may cause an undesirable delay.
In a high-speed system using the format according to a low-speed system air interface, throughput and delay time linearly increase by the increment of a data rate in the protocol stack. Further, when an ACK/NACK signal in the protocol stack is transmitted with a delay, there occurs a problem in that transmission of new data is interrupted due to the Tx window full effect. The Tx window full effect refers to the effect in which, although there is a margin in the bandwidth of the second node, the second node cannot transmit data any longer because an ACK/NACK signal in response to transmitted data is not transmitted from the first node. When this Tx window full effect occurs, there is a problem in that throughput for data transmission is lowered.